60 THE PHASES OF 



condition at least one hour. It is not necessary to use the heated 

 stage, because the colorless blood-corpuscles exhibit their struct- 

 ure in an ordinary comfortable temperature of the room nay, 

 sometimes show slight amoeboid motions. The magnifying power 

 should be at least 800 diameters, the lens to be used being best a 

 one-tenth of an inch immersion. As a matter of course, the lens 

 we use must be first-class. Considerable skill is required for 

 such studies, which embrace first the knowledge of the structure 

 of the bioplasson in general. A few months' nay, a few weeks' 

 thorough study under the direction of a reliable teacher will 

 suffice to enable every one to see what really can be seen in the 

 plastids, and to entitle him to judge also of the differences. I 

 never had difficulties in demonstrating the net- work structure of 

 the plastids to any one who was in earnest with his microscopical 

 studies, and took them for more than play. After having ob- 

 tained a certain practice, one is enabled to tell differences in the 

 anatomy of the colorless blood-corpuscles with a power of 500 

 diameters only. 



Several years ago, I was first struck by the fact that the ele- 

 ments establishing the condition of catarrhal pneumonia and of 

 tuberculosis, both acute and chronic, are decidedly pale and finely 

 granular. Next I leaTned that pus and colorless blood-corpuscles 

 of strong men are partly homogeneous, or at least coarsely 

 granular. Then I followed these studies by examining the blood 

 of different physicians who came to work in my laboratory, and 

 who could give reliable histories of both their families and their 

 own bodies. Thus I have arrived at a point of perfection which 

 allows me to tell the constitution of a person without knowing 

 anything of his former life. 



Besides the differences in the structure of the colorless blood- 

 corpuscles, as described above, valuable hints may be obtained 

 from other circumstances. The number of colorless blood-cor- 

 puscles in a given drop of blood is surprisingly different in differ- 

 ent persons; the better the constitution, the fewer are these 

 bodies. A sleepless night, however, is sufficient to increase their 

 number, which fact often enabled me to tell physicians, by exam- 

 ination of their blood, whether business was going slowly or lively, 

 the latter inducing sleepless nights, or repeated awakening by 

 patients, or so-called nervousness. 



Catarrhal processes, so-called colds, of any of the mucous 

 membranes, lead to increase of the number of the colorless blood- 

 corpuscles j a chronic condition of these processes is indicative 



